1. Field of the Invention
The present invention relates to a method of assembling a tire and a wheel, a recording medium which records a phase angle operating program at the time of assembling a tire and a wheel, and an assembled tire and wheel unit. More particularly, the present invention relates to method of assembling a tire and a wheel, a recording medium which records a phase angle operating program at the time of assembling a tire and a wheel for obtaining an optimum phase angle at the time of assembling the tire and the wheel as a predicted angle, and an assembled tire and wheel unit which is assembled in accordance with the method of assembling a tire and a wheel.
2. Description of the Related Art
Conventionally, in order to prevent vibrations of a vehicle caused by unevenness on the peripheries of a tire and a wheel due to the irregularities at the time of manufacturing the single wheel unit and the single tire unit, a positional relationship between the wheel and the tire during assemble is intentionally selected and the assembling is effected in the positional relationship. The typical method is called radial force variation (RFV) primary matching. In this assembling method, a bottom position of a Fourier primary component of radial direction vibrations (radial run-out, the mean of the front side/reverse side of the wheel) of a single wheel unit and a peak position of an RFV primary component of a single tire are matched. This is because the RFV primary component of the single tire unit after the assembling is expected to be reduced by the value of the RFV primary component caused by the vibrations of the single wheel unit.
In addition to RFV caused by the above-described small vibrations on the periphery of the tire or unevenness of rigidity, unevenness on the periphery of the tire is also caused by unevenness of mass distribution which is called unbalance. This unbalance generates centrifugal force when the assembled tire and wheel unit is rotated and causes vibrations in a vehicle by exciting an axle at the primary frequency of rotation. After the wheel and the tire are assembled, this unbalance can be theoretically cancelled by adding balance weights having accurate masses one by one to each of specific places of flange portions at the front and reverse sides of the wheel, and balancing is actually routinely effected by a method (two-surface balancing method) in accordance with this principle using a commercially-available wheel balancer.
In an operation for correcting the unevenness of the assembled wheel and tire unit to prevent the vibrations of a vehicle, basically, the two aforementioned procedures are effected in succession and the adjustment is completed when these procedures are completed. Namely, the wheel and the tire which have been adjusted are lightened by an amount corresponding to the run-out of the wheel due to the RFV primary matching of the single tire.
However, deviation (unbalance) in the entire mass distribution which is determined after the assembling may be generated on the assembled unit by the RFV primary matching, therefore a balance weight which matches the entire amount of the deviation to be rectified is forcibly added to the assembled body from an exterior.
In this way, in accordance with the RFV primary matching, the RFV of the tire is reduced using the radial direction vibrations of the wheel which is one type of unevenness of the wheel, and the wheel and the tire are thereby assembled. The unbalance accompanying the assembling method is corrected by adding the balance weight, and the assembled tire and wheel unit is obtained.
However, the amount of balance weight required for correcting the unbalance is determined by the amounts of unbalance of the wheel and the tire and the positional relationship therebetween. As a result, in the uniform assembling of the wheel and the tire called the RVF primary matching, the effect of reducing RFV is small and the amount of balance weight is excessively large. In extreme cases, when the position of a wheel, whose vibrations are very small but which has a reasonable amount of unbalance, coincidentally matches perfectly the unbalance position of the tire at the time of effecting the assembling by the RFV primary matching, the absurd outcome is that the assembling method, in which the effect of reducing RFV is almost zero and the unbalance is the worst, ends up being intentionally selected.
Further, the excessively large balance weight is not preferable because of its appearance and is counter-productive to reducing the weight of the tire. Moreover, lead has been mainly used for the balance weight, however, since the use of lead is banned for social reasons such as environmental problems or the like, iron is considered as the alternative balance weight. Nevertheless, since the specific gravity of iron is smaller than that of lead, the volume per weight thereof increases. Thus, it is desirable that the amount of unbalance itself is reduced.